The present invention relates generally to laboratory apparatus, and more particularly to an improved reagent or specimen filler which includes means for automatically wiping excess reagent from the liquid transfer tube used to measure and transfer the reagent between containers in automated analysis equipment. The present invention provides a tip wiper construction which is compatible with both rigid and resilient transfer tube tips and which avoids the shortcomings of prior art tip wiper devices and methods of the prior art.
In modern laboratory analysis, including analysis of blood serums, for example, it is very common to use sophisticated electronic equipment which is capable of analyzing such specimens before, during, or after such specimens undergo a chemical reaction with known reagents. Such analysis is typically carried out by projecting one or more light beams through a container having therein a laboratory sample, and then measuring certain physical characteristics of the specimen, such as absorption of a characteristic light frequency band, scattering of light by the specimen, or other physical phenomena.
Typically, such analysis instruments are capable of determining the presence of certain components, the concentration of such components, as well as analyzing certain characteristics of the reaction between the specimen being analyzed and standard reagents. Instruments of this type are capable of analyzing a large number of specimens in a short time with a high degree of accuracy; however, in many cases the accuracy potential of the instrument used for analysis cannot be achieved because of the presence of random error in sampling.
In other words, where the specimen itself is not capable of, or is not in fact, being handled with a given degree of accuracy, the use of a machine capable of a much higher order of accuracy is not necessary, and in some cases, may create an implication of higher accuracy than can, in fact, be attained where the samples are not accurately taken.
In a number of laboratory analysis processes, one problem is that of cross-contamination between various specimens. In other words, where a number of specimens are to be withdrawn from different containers and placed in analysis vessels, it is necessary that substantially no portion of the specimen taken from one container be introduced into another or different container. This commonly happens in laboratory equipment wherein a pipette, a dip tube, or the like is used to aspirate or withdraw the specimen from a container. Where specimens are individually pipetted, the pipette or dip tube can be cleaned by the operator. However, the speed potential of any such operation requiring repeated attention by humans is very low. On the other hand, the use of automated equipment commonly involves using the same dip tube for a plurality of specimens, and the potential for contamination between successive specimens is always present, and in certain cases, may be harmful to the accuracy of the process or may make impossible the achievement of the accuracy which the process is otherwise capable of achieving.
Accordingly, it is desired that liquid handling equipment be provided which is capable of both the speed and the accuracy potential of modern laboratory analyzers. An ideal instrument for this purpose would be one which would provide a simple and effective means of wiping excess fluid from the tip of each tube which is immersed in a laboratory specimen for the transfer of a portion thereof to an analysis vessel before the tip portion contacts the liquid in a subsequent storage vessel.
Such an ideal apparatus would be compatible with existing equipment, would include simple and effective means for wiping the tip, and could wipe the tip repeatedly without requiring attention from the operator. Ideally, the apparatus could also do so without compromising the accuracy of the measurements or imposing a physical strain on the apparatus.
In the prior art, the possibility of rinsing transfer tube tips has been considered; however, this method has certain drawbacks. Sometimes this process draws liquid from the tip, which is undesirable, and, also, rinsing requires that rinsing be carried out in an area remote from the transfer operation. It has also been proposed to dry the tips of such instruments by the use of compressed air or the like; this concept is also undesirable insofar as it may tend to disturb liquid in the interior of the tip, causing inaccuracies in volumetric measurements, and also raises the possibility of blowing droplets of liquid into other areas wherein contamination could occur.
Other proposals for tip wipers have included the provision of a sheet of paper which the tip is caused to pierce and move through; however, this is not always practical with relatively flexible tips made from plastic tubing, and, moreover, this concept potentially involves withdrawing a certain amount of fluid from the interior of tips by capillary action when the tube end meets the paper.
According to the present invention, an apparatus is provided, in a preferred form, wherein two rolls of a ribbon or tape-like absorbent paper or like material are held on reels in a supply area and trained by guide means into the vicinity of the tip, with additional means being provided for periodically advancing the ribbons from the supply reel onto a take-up reel and moving them across the tips with a wiping action each time the unit supporting the tip is moved between aspirating and discharge positions with respect to specimen and analysis containers respectively.
In view of the shortcomings of prior art devices, and the need for an improved tip wiper apparatus, it is an object of the present invention to provide an improved tip wiper apparatus.
Another object is to provide an apparatus which includes means for receiving and taking up a supply of tip wiping material in ribbon form, and which will be actuated upon movement of the tip between different operative positions thereof.
Yet another object is to provide an apparatus for wiping the tip of a specimen transferring pump apparatus which will aspirate and discharge specimens repeatedly without the need for frequent operator attention.
A further object is to provide a tip wiper apparatus which is capable of wiping the tip of a liquid transfer tube or the like without damaging the tip and without undesirably withdrawing fluid from the inside thereof.
A still further object is to provide a tip wiper apparatus which includes a pair of supply reels for tip wiping material and a take-up spool for spent material, and which can be operated in a positive manner so as to wipe the tip without requiring the additional motion devices or motion sequences in the analysis device with which the tip wiper is associated in use.
Another object is to provide a tip wiper apparatus which includes supply and take-up reels for the tip wiper material, with such reels being operated through an overrunning or other one-way clutch arrangement so as to provide positive advancement of the tip wiper material and to avoid the creation of slack or backlash in the operating unit.
A further object is to provide a tip wiper unit which includes means for supplying and taking up tip wiping material in ribbon form and which includes guideways adapted to direct material from a pair of axially spaced reels onto a common path, to guide the ribbons of material past the tip in the vicinity thereof, and to guide the material towards the take-up reel thereafter.
A still further object is to provide a tip wiper which can be used with a variety of units and which requires no additional equipment to be installed and synchronized with existing equipment.
Another object is to provide a tip wiper unit which is compatible with existing equipment and which will permit a full, uninterrupted range of tip movement without damage to the unit.
Yet another object is to provide a tip wiper unit which is capable of being supplied periodically with new reels or containers of ribbon with a minimum of difficulty, and which is arranged for simple and straightforward feeding of such material.
A still further object is to provide a tip wiper which will permit axial reciprocation of the tube while locating the tube between guide means while wiping takes place.
These and other objects of the invention are achieved in practice by providing a tip wiping apparatus which includes means adapted to receive an aspiration and discharge tip, means for receiving a supply of unused tip wiping material and for taking up a supply of used tip wiping material, means for guiding the material into the vicinity of and across portions of the tip with an effective wiping action, and means for providing an intermittent advancing motion to the wiping material so as to move it past the tip in response to movement of the tip between aspiration and discharge positions.
The exact manner in which these and other objects and advantages are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, in which like reference numbers indicate corresponding parts throughout.